1. Field of the Invention
This invention relates to current supplying pumps, and more particularly, to current supplying pumps that can dynamically change their current capability according to requirements.
2. Description of the Prior Art
Current supply pumps are standard circuits in the electronics field. They are used to supply and control an output voltage by enabling a pump, and utilizing an oscillator to control the periodicity of pump cycles. The oscillator controls the pump to pump at a desired frequency for producing a certain output voltage, and when the output voltage is too high, the pump will be disabled. These operations are controlled by a feedback mechanism.
Please refer to FIG. 1. FIG. 1 is a diagram of a conventional pump circuit 100. The pump circuit 100 comprises a limiter circuit 110, an oscillator 120 and a pump 130. The pump 130 produces an output voltage which is fed back to the limiter 110. The limiter 110 selectively outputs a pump enable signal to the oscillator 120 according to the feedback voltage. When the output of the pump 130 is too low, the limiter 110 will enable the pump signal, thereby enabling the oscillator 120, which will then cause the pump 130 to pump the output voltage higher. When the limiter 110 determines that the output voltage is high enough, the limiter 110 will disable the oscillator 120, so that the pump 130 will not pump. The oscillator 120 controls the output voltage of the pump 130 by setting the period of pump cycles.
There is therefore a correlation between the size of the output voltage and efficiency. If the current demand is high, this means that the oscillator 120 must have a higher periodicity of pump cycles. This allows the pump 130 to generate more current, but also reduces efficiency. If the oscillator 120 controls the pump 130 to pump with a reduced number of pump cycles, the efficiency increases, but there will be a cap on the amount of current the pump 130 can produce.